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921.
Kushol Gupta Tracy Diamond Young Hwang Frederic Bushman Gregory D. Van Duyne 《The Journal of biological chemistry》2010,285(26):20303-20315
Integrase (IN) is the catalytic component of the preintegration complex, a large nucleoprotein assembly critical for the integration of the retroviral genome into a host chromosome. Although partial crystal structures of human immunodeficiency virus IN alone and its complex with the integrase binding domain of the host factor PSIP1/lens epithelium-derived growth factor (LEDGF)/p75 are available, many questions remain regarding the properties and structures of LEDGF-bound IN oligomers. Using analytical ultracentrifugation, multiangle light scattering, and small angle x-ray scattering, we have established the oligomeric state, stoichiometry, and molecular shapes of IN·LEDGF complexes in solution. Analyses of intact IN tetramers bound to two different LEDGF truncations allow for placement of the integrase binding domain by difference analysis. Modeling of the small angle x-ray scattering envelopes using existing structural data suggests domain arrangements in the IN oligomers that support and extend existing biochemical data for IN·LEDGF complexes and lend new insights into the quaternary structure of LEDGF-bound IN tetramers. These IN oligomers may be involved in stages of the viral life cycle other than integration, including assembly, budding, and early replication. 相似文献
922.
Michael D. Bear Min Li Yinglin Liu Maryann A. Giel-Moloney Barry L. Fanburg Deniz Toksoz 《The Journal of biological chemistry》2010,285(43):32919-32926
Serotonin (5-hydroxytryptamine, 5-HT) is mitogenic for several cell types including pulmonary arterial smooth muscle cells (PASMC), and is associated with the abnormal vascular smooth muscle remodeling that occurs in pulmonary arterial hypertension. RhoA/Rho kinase (ROCK) function is required for 5-HT-induced PASMC mitogenesis, and 5-HT activates RhoA; however, the signaling steps are poorly defined. Rho guanine nucleotide exchange factors (Rho GEFs) transduce extracellular signals to Rho, and we found that 5-HT treatment of PASMC led to increased membrane-associated Lbc Rho GEF, suggesting modulation by 5-HT. Lbc knockdown by siRNA attenuated 5-HT-induced thymidine uptake in PASMC, indicating a role in PASMC mitogenesis. 5-HT triggered Rho-dependent serum response factor-mediated reporter activation in PASMC, and this was reduced by Lbc depletion. Lbc knockdown reduced 5-HT-induced RhoA/ROCK activation, but not p42/44 ERK MAP kinase activation, suggesting that Lbc is an intermediary between 5-HT and RhoA/ROCK, but not ERK. 5-HT stimulation of PASMC led to increased association between Lbc, RhoA, and the α-catulin scaffold. Furthermore, α-catulin knockdown attenuated 5-HT-induced PASMC thymidine uptake. 5-HT-induced PASMC mitogenesis was reduced by dominant-negative Gq protein, suggesting cooperation with Lbc/α-catulin. These results for the first time define a Rho GEF involved in vascular smooth muscle cell growth and serotonin signaling, and suggest that Lbc Rho GEF family members play distinct roles. Thus, the Lbc/α-catulin axis participates in 5-HT-induced PASMC mitogenesis and RhoA/ROCK signaling, and may be an interventional target in diseases involving vascular smooth muscle remodeling. 相似文献
923.
These experiments test whether respiration can be predicted better from biomass or from potential respiration, a measurement of the mitochondrial and microsomal respiratory electron transport systems. For nearly a century Kleiber's law or a similar precursor have argued the importance of biomass in predicting respiration. In the last decade, a version of the Metabolic Theory of Ecology has elaborated on Kleiber's Law adding emphasis to the importance of biomass in predicting respiration. We argue that Kleiber's law works because biomass packages mitochondria and microsomal electron transport complexes. On a scale of five orders of magnitude we have shown previously that potential respiration predicts respiration as well as biomass in marine zooplankton. Here, using cultures of the branchiopod, Artemia salina and on a scale of less than 2 orders of magnitude, we investigated the power of biomass and potential respiration in predicting respiration. We measured biomass, respiration and potential respiration in Artemia grown in different ways and found that potential respiration (Ф) could predict respiration (R), both in µlO2 h−1 (R = 0.924Φ + 0.062, r2 = 0.976), but biomass (as mg dry mass) could not (R = 27.02DM + 8.857, r2 = 0.128). Furthermore the R/Ф ratio appeared independent of age and differences in the food source. 相似文献
924.
Nitric oxide (NO) is known as a gaseous messenger in the nervous system. It plays a role in synaptic plasticity, but also in development and regeneration of nervous systems. We have studied the function of NO and its signaling cascade via cyclic GMP in the locust embryo. Its developing nervous system is well suited for pharmacological manipulations in tissue culture. The components of this signaling pathway are localized by histochemical and immunofluorescence techniques. We have analyzed cellular mechanisms of NO action in three examples: 1. in the peripheral nervous system during antennal pioneer axon outgrowth, 2. in the enteric nervous system during migration of neurons forming the midgut nerve plexus, and 3. in the central nervous system during axonal regeneration of serotonergic neurons after axotomy. In each case, internally released NO or NO-induced cGMP synthesis act as permissive signals for the developmental process. Carbon monoxide (CO), as a second gaseous messenger, modulates enteric neuron migration antagonistic to NO. 相似文献
925.
Georg E. Schulz 《Journal of molecular biology》2010,395(4):834-15506
The fact that aggregates of identical protein molecules are usually symmetric has remained an enigma. An idealized model of a soluble monomeric protein was constructed and accompanied through a simulated evolutionary process resulting in dimerization, in order to elucidate this peculiarity. The model showed that the probability of a symmetric association is by a factor of 100 or above higher than the probability of an asymmetric one. Unexpectedly, symmetry prevails in the dimer initiation phase much more than in the dimer improvement phase of evolution. The result is clear-cut and robust against a broad spectrum of model inadequacies. It rationalizes the predominance of symmetric homo-oligomers. 相似文献
926.
John Monsey Wei Shen Paul Schlesinger Ron Bose 《The Journal of biological chemistry》2010,285(10):7035-7044
Her4 (ErbB-4) and Her2/neu (ErbB-2) are receptor-tyrosine kinases belonging to the epidermal growth factor receptor (EGFR) family. Crystal structures of EGFR and Her4 kinase domains demonstrate kinase dimerization and activation through an allosteric mechanism. The kinase domains form an asymmetric dimer, where the C-lobe surface of one monomer contacts the N-lobe of the other monomer. EGFR kinase dimerization and activation in vitro was previously reported using a nickel-chelating lipid-liposome system, and we now apply this system to all other members of the EGFR family. Polyhistidine-tagged Her4, Her2/neu, and Her3 kinase domains are bound to these nickel-liposomes and are brought to high local concentration, mimicking what happens to full-length receptors in vivo following ligand binding. Addition of nickel-liposomes to Her4 kinase domain results in 40-fold activation in kinase activity and marked enhancement of C-terminal tail autophosphorylation. Activation of Her4 shows a sigmoidal dependence on kinase concentration, consistent with a cooperative process requiring kinase dimerization. Her2/neu kinase activity is also activated by nickel-liposomes, and is increased further by heterodimerization with Her3 or Her4. The ability of Her3 and Her4 to heterodimerize and activate other family members is studied in vitro. Her3 kinase domain readily activates Her2/neu but is a poor activator of Her4, which differs from the prediction made by the asymmetric dimer model. Mutation of Her3 residues 952ENI954 to the corresponding sequence in Her4 enhanced the ability of Her3 to activate Her4, demonstrating that sequence differences on the C-lobe surface influence the heterodimerization and activation of ErbB kinase domains. 相似文献
927.
Kanyamas Choocheep Sonoko Hatano Hidekazu Takagi Hiroki Watanabe Koji Kimata Prachya Kongtawelert Hideto Watanabe 《The Journal of biological chemistry》2010,285(27):21114-21125
Versican/PG-M is a large chondroitin sulfate proteoglycan in the extracellular matrix, which is transiently expressed in mesenchymal condensation areas during tissue morphogenesis. Here, we generated versican conditional knock-out mice Prx1-Cre/Vcanflox/flox, in which Vcan is pruned out by site-specific Cre recombinase driven by the Prx1 promoter. Although Prx1-Cre/Vcanflox/flox mice are viable and fertile, they develop distorted digits. Histological analysis of newborn mice reveals hypertrophic chondrocytic nodules in cartilage, tilting of the joint, and a slight delay of chondrocyte differentiation in digits. By immunostaining, whereas the joint interzone of Prx1-Cre/Vcan+/+ shows an accumulation of TGF-β, concomitant with versican, that of Prx1-Cre/Vcanflox/flox without versican expression exhibits a decreased incorporation of TGF-β. In a micromass culture system of mesenchymal cells from limb bud, whereas TGF-β and versican are co-localized in the perinodular regions of developing cartilage in Prx1-Cre/Vcan+/+, TGF-β is widely distributed in Prx1-Cre/Vcanflox/flox. These results suggest that versican facilitates chondrogenesis and joint morphogenesis, by localizing TGF-β in the extracellular matrix and regulating its signaling. 相似文献
928.
Boris Bryk Katrin Hahn Stephen M. Cohen Aurelio A. Teleman 《Developmental biology》2010,344(1):150-157
The TOR pathway mediates nutrient-responsive regulation of cell growth and metabolism in animals. TOR Complex 1 activity depends, amongst other things, on amino acid availability. MAP4K3 was recently implicated in amino-acid signaling in cell culture. We report here the physiological characterization of MAP4K3 mutant flies. Flies lacking MAP4K3 have reduced TORC1 activity detected by phosphorylation of S6K and 4EBP. Furthermore MAP4K3 mutants display phenotypes characteristic of low TORC1 activity and low nutrient availability, such as reduced growth rate, small body size, and low lipid reserves. The differences between control and MAP4K3 mutant animals diminish when animals are reared in low-nutrient conditions, suggesting that the ability of TOR to sense amino acids is most important when nutrients are abundant. Lastly, we show physical interaction between MAP4K3 and the Rag GTPases raising the possibility they might be acting in one signaling pathway. 相似文献
929.
Richard C. Wang 《FEBS letters》2010,584(7):1417-1426
Cell growth is regulated by two antagonistic processes: TOR signaling and autophagy. These processes integrate signals including growth factors, amino acids, and energy status to ensure that cell growth is appropriate to environmental conditions. Autophagy responds indirectly to the cellular milieu as a downstream inhibitory target of TOR signaling and is also directly controlled by nutrient availability, cellular energy status, and cell stress. The control of cell growth by TOR signaling and autophagy are relevant to disease, as altered regulation of either pathway results in tumorigenesis. Here we give an overview of how TOR signaling and autophagy integrate nutritional status to regulate cell growth, how these pathways are coordinately regulated, and how dysfunction of this regulation might result in tumorigenesis. 相似文献
930.
Youhei Sohma Qing-xin Hua Ming Liu Nelson B. Phillips Shi-Quan Hu Jonathan Whittaker Linda J. Whittaker Aubree Ng Charles T. Roberts Jr Peter Arvan Stephen B. H. Kent Michael A. Weiss 《The Journal of biological chemistry》2010,285(7):5040-5055
Proinsulin exhibits a single structure, whereas insulin-like growth factors refold as two disulfide isomers in equilibrium. Native insulin-related growth factor (IGF)-I has canonical cystines (A6—A11, A7–B7, and A20—B19) maintained by IGF-binding proteins; IGF-swap has alternative pairing (A7–A11, A6—B7, and A20—B19) and impaired activity. Studies of mini-domain models suggest that residue B5 (His in insulin and Thr in IGFs) governs the ambiguity or uniqueness of disulfide pairing. Residue B5, a site of mutation in proinsulin causing neonatal diabetes, is thus of broad biophysical interest. Here, we characterize reciprocal B5 substitutions in the two proteins. In insulin, HisB5 → Thr markedly destabilizes the hormone (ΔΔGu 2.0 ± 0.2 kcal/mol), impairs chain combination, and blocks cellular secretion of proinsulin. The reciprocal IGF-I substitution ThrB5 → His (residue 4) specifies a unique structure with native 1H NMR signature. Chemical shifts and nuclear Overhauser effects are similar to those of native IGF-I. Whereas wild-type IGF-I undergoes thiol-catalyzed disulfide exchange to yield IGF-swap, HisB5-IGF-I retains canonical pairing. Chemical denaturation studies indicate that HisB5 does not significantly enhance thermodynamic stability (ΔΔGu 0.2 ± 0.2 kcal/mol), implying that the substitution favors canonical pairing by destabilizing competing folds. Whereas the activity of ThrB5-insulin is decreased 5-fold, HisB5-IGF-I exhibits 2-fold increased affinity for the IGF receptor and augmented post-receptor signaling. We propose that conservation of ThrB5 in IGF-I, rescued from structural ambiguity by IGF-binding proteins, reflects fine-tuning of signal transduction. In contrast, the conservation of HisB5 in insulin highlights its critical role in insulin biosynthesis. 相似文献